1. Technical Field
The present invention provides a nitride-based light-emitting device, especially a nitride-based light-emitting device including a nitride-based buffer layer.
2. Description of the Related Art
The applications of light-emitting diodes are extensive, such as optical display devices, traffic signals, data storing devices, communication devices, illumination devices, and medical apparatuses. It is important to increase the brightness of light-emitting diodes, and to simplify manufacturing processes in order to decrease the cost of the light-emitting diode.
In general, a conventional nitride-based light-emitting device includes a nitride-based buffer layer composed of group AlGaInN and formed over a sapphire substrate, and a nitride-based epitaxy process is undergone on the nitride-based buffer layer to form a nitride-based light-emitting device. Due to the mismatching of the crystal lattice constants, the dislocation density (which affects the quality of the conventional nitride-based light-emitting device) cannot be decreased efficiently. Therefore, in order to improve the quality of the conventional nitride-based light-emitting device, the conventional nitride-based epitaxy process is mended as a two-step growth method, which utilizes low-temperature (500 to 600° C.) GaN for forming a buffer layer, a heating process (reaching a temperature of 1000 to 1200° C.) for crystallization, and an epitaxy process for each epitaxy stack layer. The thickness and temperature of the buffer layer, the recovery of the heating and re-crystallization processes, plus the ratio and flow rate of gas for each reaction must be controlled precisely, thus the manufacturing process becomes complicated and difficult, and as a consequence manufacturing efficiency cannot be increased.